Abstract
BackgroundNumerous studies have reported on the associations between ambient temperatures and mortality. However, few multi-city studies have been conducted in developing countries including China. This study aimed to examine the association between high temperature and mortality outcomes in four cities with different climatic characteristics in China to identify the most vulnerable population, detect the threshold temperatures, and provide scientific evidence for public health policy implementations to respond to challenges from extreme heat.MethodsA semi-parametric generalized additive model (GAM) with a Poisson distribution was used to analyze the impacts of the daily maximum temperature over the threshold on mortality after controlling for covariates including time trends, day of the week (DOW), humidity, daily temperature range, and outdoor air pollution.ResultsThe temperature thresholds for all-cause mortality were 29°C, 35°C, 33°C and 34°C for Harbin, Nanjing, Shenzhen and Chongqing, respectively. After adjusting for potential confounders including air pollution, strong associations between daily maximum temperature and daily mortality from all-cause, cardiovascular, endocrine and metabolic outcomes, and particularly diabetes, were observed in different geographical cities, with increases of 3.2-5.5%, 4.6-7.5% and 12.5-31.9% (with 14.7-29.2% in diabetes), respectively, with each 1°C increment in the daily maximum temperature over the threshold. A stronger temperature-associated mortality was detected in females compared to males. Additionally, both the population over 55 years and younger adults aged 30 to 54 years reported significant heat-mortality associations.ConclusionsExtreme heat is becoming a huge threat to public health and human welfare due to the strong temperature-mortality associations in China. Climate change with increasing temperatures may make the situation worse. Relevant public health strategies and an early extreme weather and health warning system should be developed and improved at an early stage to prevent and reduce the health risks due to extreme weather and climate change in China, given its huge population, diverse geographic distribution and unbalanced socioeconomic status with various climatic characteristics.
Highlights
Numerous studies have reported on the associations between ambient temperatures and mortality
A study in 15 European cities found that an increase of 3.12% in the Mediterranean region and 1.84% in the northcontinental region in all natural mortality was associated with a 1°C increase in the maximum apparent temperature above the city-specific thresholds
Studies conducted in California [5,6] and other parts of the USA [7] all reported that a 10°F increase in the apparent temperature was associated with approximately a 2% increase in mortality
Summary
Numerous studies have reported on the associations between ambient temperatures and mortality. Few multi-city studies have been conducted in developing countries including China. The average surface temperature of the earth has increased by approximately 0.8°C since 1900 and is projected to rise by 1.1 to 6.4°C during the hundred years [1]. The average surface temperatures in China have increased by 0.5–0.8°C over the past 100 years. Studies conducted in California [5,6] and other parts of the USA [7] all reported that a 10°F increase in the apparent temperature was associated with approximately a 2% increase in mortality. Few studies have been conducted in developing countries including China, especially large scale multi-city studies involving different climatic zones
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